pca9557_IIC python3 module

Last modification: 1.06.2021

List of python files:

Chip description The PCA9557 is 8-bit I/O expander. It consists of one 8-bit configuration (inputor output selection),input port,output port,and polarity inversion (active-high) registers.

pca9557_constant.py

list of PCA9557 chip registers and their statuses

pca9557.py

PCA9557 - main chip class
PCA9557.read_register - read status of one register
PCA9557.write_register - write new value to chip register
PCA9557.sw_reset - software Reset CHIP
PCA9557.port_init - initialize pseudo registers _iport (all input ports) and _oport (all output ports)
PCA9557.set_io - setting of port configuration (I as input pin) and (O as output pin)
PCA9557.set_invert - setting of inversion only for input pins (I as inverted) and (N as normal use or not inverted)
PCA9557.set_io_name - add to pseudo registers _iport and _oport PIN name for ease managing for developer
PCA9557.reset_inputs - set _iport pseudo register to Init status
PCA9557.reset_outputs - set _oport pseudo register to Init status
PCA9557.read_input_port - in loop reading of input PINS and set _iport register which maintains changed values ( Set for reached threshold ) and ( Unset for losing threshold)
PCA9557.write_output_port - write output value into output PIN and update _oport register ( Low for 0V ) and (High for 3.3 - 5V )
PCA9557.port_display - show in log current status of _iport and _oport pseudo registers (PIN Name, Status, Inversion, Direction)
PCA9557.port_show_name - actualise _oport and _iport registers under current status of INPUT and OUTPUT registers. ( 'i' update only _iport, 'o' update only _oport, 'io' update both)

for internal use:

PCA9557.set_bit - change bit in byte to 1
PCA9557.get_bit - read bit in byte
PCA9557.unset_bit - change bit in byte to 0

How to call python sub?

see pca9557_i2c_test.py script located in python_test_scripts directory

set logging:

logging.basicConfig(level=logging.INFO

set for INFO level logging. possible used DEBUG, ERROR loogin script will produce log pca9557.log

initialize chip:

sens = pca9557.PCA9557()

sw reset:

ret = sens.sw_reset()     # make sw reset of chip !!necessary command before start CHIP connecting!!

default setting of REGISTERs

return value: (<ret>)

ret = 0 -> correct setting REGISTERS, ret > 0 -> issue during setting

read from register:

value = sens.read_register(register = <command>)[0]

register parameter is name of chip register ('REGISTER0-3')

return value: (<8bit value>, <ret>)

first return parameter is content of register
ret = 0 -> correct writing into register, ret > 0 -> issue during reading process

write to register:

ret = sens.write_register(register = <command>, value = <variable>)

register parameter is name of chip register ('REGISTER0-3'), value is 8bit value written into register

return value: (<ret>)

ret = 0 -> correct writing into register, ret > 0 -> issue during writing process

port_init:

self.port_init()

initialize pseudo registers _iport (all input ports) and _oport (all output ports) both registers are object registe that you can directly manage which are set to default values during object init. it's array of 8 items (for each PIN one array)

[10,Sleep,'X-------',NI] #[<pin number>,<pin status>,<pin name>,<pin inversion>

<pin number>
- from 0 - 7 coresponded to chip pin number P0-P7, default value 10 means no existing pin
<pin status>
- Sleep - INPUT-OUTPUT (pin is not initialized) -> could not read or write to it
- Init - INPUT-OUTPUT (pin is initialized) -> prepared for reading or writing to it
- Measure - INPUT (prepared for measure input pin)
- Threshold - INPUT (pin reached threshold value)
- High - OUTPUT (pin set to logical value 1)
- Low - OUTPUT (pin set to logical value 0)
<pin name>
- INPUT-OUTPUT use word without space and other special characters, only _ character is accepted
<pin inversion>
- Invert - INPUT pin is inverted
- Normal - INPUT pin si not inverted
- NoAppl - OUTPUT inversion is not applicable

Values of pin statuses are constant of pca9557.py library sub port_init is called internally by port_io sub, but could be used also externally

return value: (0)

0 -> correctly initialized

set_io:

set_io(<pattern>)
# example
set_io('OOIIIIOO')

setting of port configuration (I as input pin) and (O as output pin) at end of def is called port_init()

return value: (<mask_byte>,<ret>)

mask_byte - byte O->0, I->1 used for REGISTER3 (is already set in def)
ret = 0 -> correct writing into register, ret > 0 -> issue during reading process

set_invert:

set_invert('<pattern>')
#example
set_invert('NNNNNNNI')

setting of inversion only for input pins (I as inverted) and (N as normal use or not inverted)

return value: (<mask_byte>,<ret>)

mask_byte - byte N->0, I->1 used for REGISTER3 (is already set in def)
ret = 0 -> correct writing into register, ret > 0 -> issue during reading process

set_io_name:

set_io_name(port_arr=<array>)
#example
sens.set_io_name(port_arr = [[0,'LED1'],[1,'LED2'],[2,'BUT_RIG_DWN'],[3,'BUT_RIG_UP'],
                             [4,'BUT_LFT_DWN'],[5,'BUT_LFT_UP'],[6,'DIS_RST'],[7,'D/C']])

add to pseudo registers _iport and _oport PIN name for ease managing for developer

array: 8 items
- <port_number> (0-7)
- <port_name> 'string'

return value: (0)

0 -> correctly initialized

reset_inputs:

reset_inputs()

set _iport pseudo register to Init status

set _iport register set all named inputs to default status status ['Init']

reset_outputs:

reset_outputs()

set _oport pseudo register to Init status

set _oport register set all named outputs to default status status ['Init']

read_input_port:

interrupt = sens.read_input_port(thr = 'Unset', mtime = 6, offset = 0.5)

in loop reading of input PINS and set _iport register which maintains changed values ( Set for reached threshold ) and ( Unset for losing threshold)

mtime = max time of loop length in [seconds]
offset = waiting time after catching first input threshold (waiting for multiple touching inputs) in [seconds]

example:

PIN	Name	Status	Note
2	BUT_RIG_DWN	Measure
3	BUT_RIG_UP	Measure
4	BUT_LFT_DWN	Threshold	<- catched pin
5	BUT_LFT_UP	Measure

ecomet.pca9557: INFO     PIN0: 2 : 3 : BUT_RIG_DWN
ecomet.pca9557: INFO     PIN1: 3 : 3 : BUT_RIG_UP
ecomet.pca9557: INFO     Loop:0 -> PIN4: BUT_LFT_DWN ... pushed
ecomet.pca9557: INFO     PIN2: 4 : 4 : BUT_LFT_DWN
ecomet.pca9557: INFO     PIN3: 5 : 3 : BUT_LFT_UP
ecomet.pca9557: INFO     PIN4: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN5: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN6: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN7: 10 : 20 : X-------

return value: (<_iport>)

array of values [<pin_number>,<pin_status>,<pin_name>]

write_output_port:

write_output_port (status = <pin_output_status>, pin = <pin_name>)
#example
sens.write_output_port (status = pca9557.Low, pin = 'LED1')

write output value into output PIN and update _oport register ( Low for 0V ) and (High for 3.3 - 5V )

status = pin output status
- Low = 0V
- High = 3.3 - 5V

return value: (<_oport>,<ret>)

array of values [<pin_number>,<pin_status>,<pin_name>]
ret = 0 -> correct writing into register, ret > 0 -> issue during reading process

port_display:

sens.port_display()

Show current status of _iport and _oport pseudo registers that collect more information about PINs (no actual status, but last actualised or measured or set).

For pins:
- Name:
  - User defined name, no space char allowed
- Status:
  - Sleep - not initialized
  - Init - initialized and waiting for Input action
  - Thresh. - threshold measure means reached Set or Unset at INPUT pins - ( Inversion will replace reaching Set as 0 at INPUT pin, or as 1 at INPUT pin when normal inversion )
- Invert:
  - NoAppl - when PIN is set as OUTPUT inversion mode is not used (Not Applicable)
  - Invert - INPUT pin is inverted, threshold is 1->0
  - Normal - INPUT pin is in normal, threshold is 0->1

example:

PIN	Name	Status	Invert	Direction
PIN0	LED1	High	NoApl	OUTPUT
PIN1	LED2	Low	NoApl	OUTPUT
PIN2	BUT_RIG_DWN	Thresh.	Normal	INPUT
PIN3	BUT_RIG_UP	Init	Normal	INPUT
PIN4	BUT_LFT_DWN	Init	Normal	INPUT
PIN5	BUT_LFT_UP	Init	Invert	INPUT
PIN6	DIS_RST	Init	NoApl	OUTPUT
PIN7	D/C	Init	NoApl	OUTPUT

PIN0-1 and PIN6-7 are OUTPUTs,
PIN2-5 are INPUTs, buttons
PIN0-1 are LED pins used for LED lighting, LED1 is ligh is dimmed, LED2 light is off
PIN2 detect pushed button
PIN3-5 buttons are not pushed, PIN5 check status 1->0
PIN6 and PIN7 was not currently set and are off (Low value is difault value), status will change after writing new status in _oport

output of test script:

pi@raspberrypi:~/ecomet_i2c_raspberry_tools $ python3 pca9557_i2c_test.py
3.7.3 (default, Jan 22 2021, 20:04:44)
[GCC 8.3.0]
ecomet.pca9557: INFO     Start logging ...
ecomet.pca9557: INFO     Show Ports:
ecomet.pca9557: INFO     PIN0: LED1 : OUTPUT : 3
ecomet.pca9557: INFO     PIN1: LED2 : OUTPUT : 3
ecomet.pca9557: INFO     PIN2: BUT_RIG_DWN : INPUT : 2
ecomet.pca9557: INFO     PIN3: BUT_RIG_UP : INPUT : 2
ecomet.pca9557: INFO     PIN4: BUT_LFT_DWN : INPUT : 2
ecomet.pca9557: INFO     PIN5: BUT_LFT_UP : INPUT : 2
ecomet.pca9557: INFO     PIN6: DIS_RST : OUTPUT : 3
ecomet.pca9557: INFO     PIN7: D/C : OUTPUT : 3
ecomet.pca9557: INFO     Push 10 times any Button ....
ecomet.pca9557: INFO     PIN0: 2 : 3 : BUT_RIG_DWN
ecomet.pca9557: INFO     PIN1: 3 : 3 : BUT_RIG_UP
ecomet.pca9557: INFO     Loop:0 -> PIN4: BUT_LFT_DWN ... pushed
ecomet.pca9557: INFO     PIN2: 4 : 4 : BUT_LFT_DWN
ecomet.pca9557: INFO     PIN3: 5 : 3 : BUT_LFT_UP
ecomet.pca9557: INFO     PIN4: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN5: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN6: 10 : 20 : X-------
ecomet.pca9557: INFO     PIN7: 10 : 20 : X-------
ecomet.pca9557: INFO     Show Ports:
ecomet.pca9557: INFO     PIN    Name            Status          Invert          Direction
ecomet.pca9557: INFO     -----------------------------------------------------------------------------------------
ecomet.pca9557: INFO     PIN0:  LED1 :          Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN1:  LED2 :          Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN2:  BUT_RIG_DWN :   Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN3:  BUT_RIG_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN4:  BUT_LFT_DWN :   Thresh. :       Normal :        INPUT
ecomet.pca9557: INFO     PIN5:  BUT_LFT_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN6:  DIS_RST :       Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN7:  D/C :           Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     Show Ports:
ecomet.pca9557: INFO     PIN    Name            Status          Invert          Direction
ecomet.pca9557: INFO     -----------------------------------------------------------------------------------------
ecomet.pca9557: INFO     PIN0:  LED1 :          Low     :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN1:  LED2 :          High    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN2:  BUT_RIG_DWN :   Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN3:  BUT_RIG_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN4:  BUT_LFT_DWN :   Thresh. :       Normal :        INPUT
ecomet.pca9557: INFO     PIN5:  BUT_LFT_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN6:  DIS_RST :       Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN7:  D/C :           Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     Show Ports:
ecomet.pca9557: INFO     PIN    Name            Status          Invert          Direction
ecomet.pca9557: INFO     -----------------------------------------------------------------------------------------
ecomet.pca9557: INFO     PIN0:  LED1 :          High    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN1:  LED2 :          Low     :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN2:  BUT_RIG_DWN :   Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN3:  BUT_RIG_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN4:  BUT_LFT_DWN :   Thresh. :       Normal :        INPUT
ecomet.pca9557: INFO     PIN5:  BUT_LFT_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN6:  DIS_RST :       Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN7:  D/C :           Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     Show Ports:
ecomet.pca9557: INFO     PIN    Name            Status          Invert          Direction
ecomet.pca9557: INFO     -----------------------------------------------------------------------------------------
ecomet.pca9557: INFO     PIN0:  LED1 :          High    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN1:  LED2 :          High    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN2:  BUT_RIG_DWN :   Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN3:  BUT_RIG_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN4:  BUT_LFT_DWN :   Thresh. :       Normal :        INPUT
ecomet.pca9557: INFO     PIN5:  BUT_LFT_UP :    Init    :       Normal :        INPUT
ecomet.pca9557: INFO     PIN6:  DIS_RST :       Init    :       NotApl :        OUTPUT
ecomet.pca9557: INFO     PIN7:  D/C :           Init    :       NotApl :        OUTPUT
R0 = 63
R1 = 3
R2 = 0
R3 = 60

Note: for more details look into pca9557_i2c_test.py

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pca9557_python.IIC.md

pca9557_python.IIC.md

pca9557_IIC python3 module

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How to call python sub?

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pca9557_IIC python3 module

List of python files:

How to call python sub?